Electromagnet



July 20 1926. 1,593,384 7 H. W. BROWN ELECTROMAGNET Filed Feb. 13, 1926 Inventor": Ham/a Erawn,

Patented July 20, 1926.

UNITED STATES PATENT OFFICE.

HAROLD W. BROWN, 01' SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEG- TRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTROMAGNET.

Application filed February 18, 1928. Serial No. 88,184.

My invention relates to improvements in I electromagnets, and more particularly to improvements in electromagnets for electroresponsive devices, such as rotective relays, whereby desired changes in the operation of the device, such as the relation between the currents necessary to attract and release an electromagnetically actuated member and the value of the current necessary to attract the member, are greatly facilitated.

My invention will be better understood from the following description taken in connection with the accompanying drawing,

, and its sco e will be pointed out in the appended c aims.

'In the accompanying drawing, Fig. 1 illustrates in a sectional view an electromagnet embodying my invention, and Fig. 2

is a view of the armature shown in Fig. 1, looking upward, certain parts being omitted for clearness. r

In time element relays, havin a time limit device whose operation is initiated and controlled by the movement of an electromagnetically actuated member, such as an armature, in response to a predetermined condition, for example, currents twenty-five r cent in excess of normal, no harm is done if this excess current does not last too long, but, even though it lasts for less than the dangerous period, and returns to normal, unless the armature is released promptly so as to stop the timing, an unnecessary circuit interruption may occur. .In the application of electromagiets to relays, it is, therefore, very desirable, not only for adjustment, but also for assembling and testmg, to

tion between the currents that will attract and release the armature, and also to control the value of the current necessary to attract the armature.

In accordance with my invention, I provide an electromagnet comprising an energizing winding 3 and relatively fixed and movable cooperating magnetic elements 4 and 5, respectively. The fixed magnetic element 4 is shown as the yoke or body of the magnet, and is provided with an adjustably mounted hollow pole piece 6. The movable magnetic element 5 is shown as the armabe able readily to control the rela- P ture. This comprises a plurality of magnetic members 5, 7 and 8, which are adapted for relative movement so as to permit changes in the shape of the armature. The main or body portion 5 of the armature may be of hollow cylindrical form. For increasing the value of the current at which the armature is released, that is to say, increasing the drop-out point, the lower part of the armature portion 5 may be arranged to have a diminishing cross-section so as to increase the reluctance of the magnetic circuit as the armature moves to the attracted position. This may be done by cutting away portions of the armature as indicated in Fig. 2, so that it has somewhat the shape of the frustrum of a pyramid, cylindrical portions 9 being left for alining the armature in its movement through the non-magnetic guide ring 10 which is mounted in .a non-magnetic bushing 11.

In order-to maintain the parts 5, 7 and 8 of the armature in any given position, and yet be able to change the shape of the armature so as to change the operating characteristic of the electromagnet, the

parts 5, 7 and 8 are secured together as a unit by means permitting relative movement and comprising an actuating member such as a non-magnetic rod 12 and a joinin member such as a hollow member or tu e 13, which is referably non-magnetic. In order to be ab e to change the amount of current necessary to attract the armature, that is, the ick-up point, there is secured to one end 0 the tube 13 the magnetic member 7, and the tube passes through the body portion 5 of the armature freely at the uper end, while the lower end is threaded into the base of the portion 5. Conseqently, by changing the portion 5 relative y to the tube 13, the gap between the portions 5 and 7 can be varied so as to change the reluctance of the circuit. Suitable means, such as a lock nut 14, may be provided to prevent relative movement of the armature 5 and tube 13 when positioned as desired.

The actuating rod 12 may be connected at its upper end, which passes through a guide plate 15, to a contact controllln mechan sm, a mechanism, or the e. Se-

osition of the armaturecured to the rod 12 is the magnetic member 8, whose position relatively to the magnetic member 7 ma be varied so as to c ange the shape of t e armature ole piece which cooperates with the pole iece 6. In order to change the relative posltion of the members 7 and 8, so as to vary the ratio between the currents at which the armature will be attracted and released, the actuating rod 12 extends through the magnetic member 7 and the tube 13 Into the lower end of which it is threaded. Suitable means, such as a lock nut 16, may be provided to prevent relative movement of the tube 13 and the rod 12, that is to say, the magnetic members 7 and 8, when positioned as desired.

The magnetic members 7 and 8, which from the armature pole piece, may be arranged to slide one within the other, and their shapes ma be, as illustrated, in art cylindrical an in part frusto-conlcal. Consequently, as they are moved relatively to each other, their effective composite shape may be varied considerably from a comaratively blunt-nosed pole piece to one that 1s relatively pointed or sharp.

The eflect of the magnetic member or pole iece tip 8 is to add to the initial attractive orce, but when the armature reaches a certain position, the ull, due to the flux, .between the tip 8 and the stationary pole piece 6 into which it projects, becomes substanitally zero, so that the increased eflectof the tip is eliminated. Obviously, the farther the tip 8 projects from themember 7, that is, the sharper the general contour of the armature pole piece, "the greater the initial attractive force, but the quicker the eflect of the ti becomes substantially zero. By var ing t e shape of the armature pole iece in t is way, the relation between the pic -up and drop-out current values may be readily varied. Moreover, the value of current necessary to pick up the armature may be varied by changing the relative position of the armature 5 and the ma netic member 7 as heretofore described. Since all these changes can be made by merely working on the parts at the lower end of the magnet, it is unnecessary to take the electromagnet apart or disconnect the rod 12 from the mechanism'it controls. Facility in controlling the characteristic of the electromagnet for difierent redetermined operatin conditions is assured? While have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangement shown, but seek to cover in theap nded &

claims all those modifications that fa within the true spirit and scope of my inven- What I claim as new, and desire to secure by Letters Patent of the United States, is: 1. An electromagnet comprisinga winding, a pole piece, an armature, and means carried by the armature tor varying the ratio between the currents in said winding at which the armature will be attracted to and released from said pole piece, and com prising a cooperating pole piece having a plurality of magnetic members arranged for relative movement whereby the shape of the pole piece can be varied in accordance with the relative position of the members.

2. An electromagnet comprising a winding, a pole iece, an armature and means carried by t e armature for varying the ratio between the currents in said winding at which the armature will be attracted to and released from said pole piece, and comprising a cooperating pole piece having a plurality of magnetic members arranged for relative movement whereby the shape of the pole piece can be varied in accordance with the relative position of the members, said cooperating pole piece and said armature being relatively movable whereb the p081- tion of one relatively to the ot or can be changed to vary the value of the current necessary in said winding to attract the armature.

3. An electromagnet comprising an energizing winding, a pole piece, an armature comprising a body portion and means for varying the ratio between the currents in said winding at which the armature will be attracted to and released from said 10 piece comprising a cooperatin pole piece having a lurality of magnetic members arranged or relative movement, whereby the. shape of the cooperating le piece can be varied in accordance wit the relative positlon of the members, and means for va mg the position of said cooperating po 0 piece relatively tocthe body portion of the armature whereby to vary the value of the current necessary in said winding to attract thgI azmatlure. l I

n e ectromagnet com ri re ative fixed and movable magneti; e l d n ients char acterized by the fact that one of said elements is provided with a le piece comprising a plurality of magnetic members adapted to have their relative positions varied whereby to change the shape of the pole piece.

5 An elggtromagnet comprising an energizing win ng and an armature comprising a plurality of magnetic members adapted for re ative movement whereby to permit changes in the shape of the armature.

6. An electroma et comprising a winding, a pole piece an an armature, and means or varying the relation between the currents in said winding at which the armature will be attracted to and released from said le piece comprising a cooperating pole piece avmg a plurality of magnetic members arranged for relative movement whereby the shape of the cooperating pole piece can be Ill varied in accordance with the relative positions of the members.

7. An electromagnet comprising a winding, an armature, and means for varying the relation between the currents in said winding at which the armature will be attracted and released comprising a pole piece having a plurality of magnetic members arranged for relative movement whereby the shape of the pole piece can be varied in accordance 10 with the relative position of the members.

In witness whereof, I have hereunto set my hand this 12th da of February, 1926.

HXROLD W. BROWN. 

